Help!!!

I’m hoping to not be pregnant, I’m 17 and I had sex a few weeks ago. I know he didn’t cum in me, because he stopped early and made sure, I watched. I am 3 days late right now. I haven’t been exercising at all because I’ve been hurt. But for the last 2 weeks I am no longer hurt so I’m exercising way more, could increased exercise be affecting it to be late? I also have been super stressed lately. But I’m never usually late on a period. I do have sore breasts but that’s about it. My periods have been quite irregular too, since I took plan B a few months ago. Could I be pregnant or am I just freaking out!? What are causes of it to be late!